Benzoxazole compounds useful as optical brightening agents

ABSTRACT

BENOXAZOLE COMPOUNDS OF THE GENERAL FORMULA   2-(R1,R2,R5-4,5-DIHYDRONAPHTHO(1,2-B)THIOPHEN-2-YL),R3,R4-   BENZOXAZOLE   IN WHICH R1 AND R2 STAND FOR HYDROGEN, HALOGEN, ALKYL GROUPS, OR TOGETHER STAND FOR THE RESIDUAL MEMBERS OF A CYCLOALIPHATIC RING; R3 DENOTES HYDROGEN, HALOGEN, AN ALKYL, CYCLOALKYL, ARALKYL, ARYL, CARBOXYLIC ACID ESTER, CARBOXYLIC ACID AMIDE, ALKYLSULPHONYL, ARYLSULPHONYL RADICAL, OR AN AMINOSULPHONYL RADICAL; R4 STANDS FOR HYDROGEN OR AN ALKYL RADICAL; R3 AND R4 TOGETHER MAY ALSO BE THE RESIDUAL MEMBERS OF A CYCLOALIPHATIC RING; AND R5 DENOTES AN ALKYL RADICAL OR HYDROGEN, AS WELL AS THEIR PREPARATION AND THEIR USE AS OPTICAL BRIGHTENING AGENTS.

Patented Jan. 15, 1974 The new benzoxazole compounds of the Formula I 3786 064 are re ared, f 1 b BENZOXAZOLE CbMi OUNDS USEFUL As of tie tiormular examp e, y condensing carboxylic acids OPTICAL BRIGHTENINGAGENTS Horst Harnisch, Cologne, Germany, assignor to BayerAktiengesellschaft, Leverkusen, Germany 5 N0 Drawing. Filed Apr. 1,1970, Ser. No. 24,860 I Claims priority, application Germany, Apr. 5,1969, 000K P 19 17 601.3; 0ct.25, 1969,P 19 53 809.1

Int. Cl. (107d 85/48 1 Us. or. 260-307 D 8 Claims R ABSTRACT on THEDISCLOSURE an Benzoxazole compounds of the general formula m whlch 5 R Rand R have the same meaning as above, or their Ra functionalderivatives, with aminophenols of the m /N formula 8 a 1 0 R 20 HzN(III) in WhlCh R and R stand for hydrogen, halogen, alkyl groups, ortogether stand for the residual members of m Whlch a cycloaliphaticring; R denotes hydrogen, halogen, an R3 and 4 have the same meaning asabove alkyl, cycloalkyl, aralkyl, aryl, carboxylrc acid ester, car- 1boxylic acid amide, alkylsulphonyl, arylsulphonyl radical, i y mpresence an Flcldlc i sflch or an aminosulphonyl radical; R stands forhydrogen or bone acld acld Q Z1116 Fhlorlde, 111 an alkyl radical; R andR together may also be the the melt or optlonilny m an Inertltlgh'boihng organic residual members of a cycloaliphatic ring; and Rdenotes f Such dlchlombenzelie" mchloro'benmne X an alkyl radical orhydrogen, as well as their preparation dllnethyl formamldie propylene qand their use as optical brightening agenm ethylene glycol drethyl etheror methylene glycol diethyl ether, at temperatures of about 160 to 300C. 5 In some cases, especially if R is a metadirecting substit- Thesubject-matter of the present invention comprises uent, such as e.g. adialkylamino-sulphonyl radical, it is valuable, new, fluorescent,virtually colorless benzoxazole advisable first to prepare from thecarboxylic acid of the compounds of the general formula Formula II andthe aminophenyl of the Formula III, at

140 to 200 C., the amide of the formula R 40 N u L I I NH s R 0 s s g lR H0 R (1) R in which (IV) R and R are identical or diiferent and standfor hydroin which g g alkyl groups, or together Stand for the R to Rhave the same meaning as above,

residual members of a cycloaliphatic 5- or G-membered ring; R3 denoteshydrogen, halogen, an alkyl, cyc1o and then to convert the latter, W1thor without intermedialk 1, aralk 1, ar 1 carbox lie acid ester, carboxMC ate isolation, with the aid of a dehydrating agent, such as acic lamide, alkyl sulphonyl, arylsulphonyl radical or phosphorus miychlondevglyphqsphoric an amino-sulphonyl radical preferably substituted by acld(150170 or bone and (240'300 Into the alkyl radicals; R stands forhydrogen or an alkyl radibenzlmazole compolinds 9 the Formula cal; R3and R4 together may also be the residual mam Suitable carboxyhc acids ofthe Formula II are, for bwS of a cycloafiphatic or 6 membered ring; andexample, the compounds of the Formula V listed III the R denotes analkyl radical or hydrogen, following table:

Compounds of the formula as Well as their production and their use asoptical brightening agents. H

The compounds of the Formula I are suitable for the R5 brightening ofnatural fibres or fabrics such as wool or cellulose, but particularlyfor the brightening of fibre COOH materials, foils and masses ofsynthetic origin, for example, those made of polyvinyl compounds, suchas polyvinyl chloride or polyvinyl acetate, polystyrene, polyolefines,such as polyethylene or polypropylene, polymers containingacrylonitrile, and of those made of cellulose l esters, polyamides,polyurethanes and aromatic polyesters.

TABLE R R R R CH3 H H H z s H H H H H H H H H CH3 H H H H CH3 H H H02115 H H H (CH3)2CH H CH: H CH3 H H CH3 CH3 H Cl H H H H 01 H H H H ClH Cl H 01 H H F H H B! H H Other suitable compounds of the Formula IIare, for

example 00011 and i i SJ-COOH The carboxylic acids of the Formula II canbe obtained, for example, by hydrolysis of their ethyl esters which canbe prepared by the method described in Tetrahedron Letters 1968, 1317,from a-tetralone derivatives via the stage of the correspondingchloraldehydes.

Examples of suitable aminophenols of the Formula III are:

1-amino-2-hydroxy-benzene 1-amin0-2-hydroxy-4-methylbenzene1-amino-2-hydroxy-S-methylbenzene 1-amino-2-hydroxy-3,S-dimethylbenzene1-amino-2-hydroxy-4,S-dimethylbenzene1-amino2-hydroxy-5-tert.-butylbenzene 1-amino 2-hydroxy-5-( 1',1,3,3'-tetramethyl) butylbenzene 1-amino-2-hydroxy-5 B-cyanoethyl) -benzene1-amino-2-hydroxy-(fl-methoxycarbonylethyl)-benzene1-amino-2-hydroxy-S-cyclohexylbenzene 1-amino-2-hydroxy-5 chlorobenzene1-amino-2-hydroxy-5-fluorobenzene 1-amino-2-hydroxy-benzene-5-carboxylicacid methyl ester l-amino-Z-hydroxy-benzene-S-carboxylic acid methylester 1-aminc-2-hydroxy-benzene-S-carboxylic acid isobutyl ester1-amino-Z-hydroxy-benzene-S-carboxylic acid benzyl ester1-amino-2-hydroxy-benzene-5-carboxylic acid allyl ester1-amino-2-hydroxy-benzene-5-carboxylic acid diethylamide1-amino-2-hydroxy-benzene-S-carboxylic dimethylamide1-amino-2-hydroxy-benzene-S-carboxylic acid morpholide1-amino-2-hydroxy-benzene-5-carboxylic acid dimethyl hydrazide5-amino-6-hydroxy-indane 1-amino-2-hydroxy-5-benZyl-benzene1-amino-2-hydroxy-5 phenylisopro pyl) -benzenel-amino-2-hydroxy-5-phenyl-benzene1-amino-2-hydroxy-S-phenylsulphonyl-benzene1-amino-2-hydroxy-S-methylsulphonyl-benzene1-amino-Z-hydroxy-S-ethylsulphonyl-benzene1-amino-2-hydroxy-S-aminosulphonyl-benzene1-amino-2-hydroxy-5-dimethylamino-sulphonyl-benzene1-amino-2-hydroxy-S-diethylamino-sulphonyl-benzene1-amino-2-hydroxy-di-n-butylamino-sulphonyl-benzene1-amino-2-hydroxy-(piperidyl-N-sulphonyl)-benzene A particularlyvaluable group of benzoxazole compounds within the scope of the GeneralFormula I corresponds to the formula in which Z denotes hydrogen,halogen, an alkyl, cycloalkyl, aralkyl,

aryl, carboxylic acid ester, alkylsulphonyl or dialkylamino-sulphonylradical; Z stand for hydrogen or a lower alkyl radical; and Z denotes amethyl group or hydrogen.

The compounds of the Formula I can be used as optical brightening agentsin the usual way, for example in the form of aqueous dispersions,suitable dispersing agents being, inter alia, oleyl polyglycol ethers orcondensation products of naphthalene-sulphonic acids and formaldehyde.

The brightening agents can also be applied with advantage from organicsolutions, for example, those in which water-immiscible solvents, suchas tetrachloroethylene, trichloroethylene, 1,1,l-trichloroethane or1,1,1-trichloropropane are used. In these solvents, even the simplestrepresentatives of the compounds according to the invention, without theaid of established solubilizing substituent such as tertiary butylgroups, have a good solubility in the cold, as is required for thepreparation of clear padding liquors for the continuous dyeing ofsynthetic fibre materials.

The brightening agents can also be used together with detergents.Furthermore, they can be added to spinning and casting masses servingfor the production of synthetic fibres, filaments, foils and othermoulded articles.

The compounds of the present invention are very productive brighteningagents and have an excellent range of application, on account of theirgood solubility; they are moreover fast to light and also fast tochlorite-containing bleaching baths. The benzoxazole compounds hithertoproposed a brightening agents do not have these advantageous propertiesto the same extent.

The parts given in the following examples are parts by weight; thetemperatures are given as degrees Centigrade.

EXAMPLE 1 23 parts 4,5 dihydronaphtho- [1,2-b]-thiophen-2-carboxylicacid of melting point 208-211, prepared by hydrolyzing the ethyl esterdescribed in Tetrahedron Letters 1968, 1317, for 3 hours with a 3%sodium hydroxide solution and subsequent acidification, are heated with15 parts 1-amino-Z-hydroxy-S-methylbenzene and 1 part boric acid in 60parts diethylene glycol diethyl ether under a weak nitrogen current at-190" for 1 hour while stirring, and subsequently heated at 230 for 30minutes and at 230 for a further 30 minutes, the liquid being distilledoff at the same time. The hot melt is then mixed at 170 while stirringwith 30 parts dimethyl formamide and at 90 with 300 parts methanol, andtirred on an ice bath until cold. The resultant crystalline precipitateis filtered 011' with suction, Washed with methanol, and dried in avacuum at 50. 24.1 parts of the compound of the formula and of meltingpoint 112-115 are obtained. After recrystallization from toluene(clarification with tonsil and active charcoal), the compound has amelting point of 115-1l7 (slight greenish yellow needles).

The following compounds are prepared in an analogous way with the use ofthe corresponding starting compounds:

melting point: 143-145" melting point: 175177 melting point: 115-117 I ls melting point: 167-169 melting point 152-154 EXAMPLE 2 24.4 partsS-methyl-4,5-dihydronaphtho [1,2-b] thiophen-Z-carboxylic acid ofmelting point 195-197 prepared by hydrolyzing the ethyl ester preparedin analogy with Tetrahedron Letters 1968, 1317, for 2 hours with a 5%sodium hydroxide solution and subsequent acidification, are heated with12 parts l-amino-2hydroxybenzene and 2 parts boric acid in 40 partsdiethylene glycol diethyl ether under a weak nitrogen current, Whilestirring and distilling oif the liquid, at 180-190 for 45 minutes, at190-210 for 15 minutes, and at 230-240 for 30 minutes. The hot melt ismixed with 150 parts by volume ethanol, starting at 120 and coolingunder reflux, and stirred on an ice bath until cold. The resultantcrystalline precipitate is filtered oflF with suction, washed withethanol, and dried in a vacuum at 50. 16.5 parts of the compound of theformula Win EXAMPLE 3 23 parts 4,5-dihydronaphtho [1,2 b] thiophen-Z-carboxylic acid, 25 parts l-amino-Z-hydroxy S (phenylisopropyl)-benzeneand 2 parts boric acid are heated under a weak nitrogen current, whilestirring and distilling oil the liquid, at 200 C. for 30 minutes, andthen at 250 for 30 minutes. The melt is mixed at 200 with 30 partsdimethyl tormamide and at under reflux With 70 parts methanol, andstirred on an ice-bath until cold. The resultant crystalline precipitateis filtered off with suction, washed with alcohol, and. dried in avacuum at 60. 24 parts of the compounds of the formula N i t Oss meltingpoint: 104-106 EXAMPLE 4 4.5 parts 5-methyl-4,S-dihydronaphtho [1,2-b]thiophen-2-carboxylic acid of melting point 195-197", 6 parts1-amino-2-hydroxy-S-phenyl-benzene and 0.5 part boric acid are heated in10 parts diethylene glycol diethyl ether under a weak nitrogen current,while stirring and distilling oil the liquid, at -190" for 45 minutes,at -210 for 30 minutes, and at 310-320" for 15 minutes. The hot melt ismixed with 10 parts dimethyl formamide, starting at 170, and with 70parts ethanol, starting at 90 and cooling under reflux, and then stirredon an ice bath until cold. The resultant crystalline precipitate isfiltered off with suction, washed with ethanol, and dried in a vacuum at50.

There are obtained 5.6 parts of the compound of the formula H on; N

which is purified by dissolving it in hot benzene, clarification withtonsil, cooling, separating 0.7 part of an impure fraction, andconcentration. The pure Compound melts at 107-108. It has an even bettersolubility in perchloroethylene than the methyl-free compounds of theformula which is prepared in an analogous way and melts at 159.5-160".

EXAMPLE 5 23 parts 4,5-dihydronaphtho-[1,2-b]-thiophen-2-carboxylic acidof melting point 210-212, 21 parts l-amino-2-hydroxy-5-ethylsulphonyl-benzene and 2 parts boric acid are heated in40 parts diethylene glycol diethyl ether under a weak nitrogen current,while stirring and distiling olf the liquid, at 180190 for 60 minutesand at 200 for 20 minutes. The melt is mixed with 100 parts ethanol,starting at 120 and cooling under reflux, and then stirred on an icebath until cold. The resultant crystalline precipitate is filtered offwith suction, washed with ethanol, and dried in a vacuum at 50. 30.3parts of the compound of the formula S 0 2C 2H5 S \NH/ and of meltingpoint 236237 (from benzene) are ontained.

4 parts of the compound of the Formula 12 are heated in 20 partsphosphorus oxychloride for minutes at boiling temperature while stirringand cooling under reflux; a clear yellowish solution is formed afterabout 5 minutes. The mixture is then cooled and poured on to 200 g. ofice while stirring. A pH value of about 3-4 is subsequently adjusted bythe addition of a saturated sodium acetate solution. The resultantcrystalline precipitate is filtered off with suction, washed with waterand recrystallized from alcohol while still moist. 3 parts of thecompound of the formula N SO2CzH5 and of melting point 172173 areobtained.

The following compounds are prepared in an analogous 8 way with the useof the corresponding starting com pounds:

N I I I SOz-C Hu melting point: 204-205 melting point: 184-185 EXAMPLE 623 parts 4,5-dihydronaphtho-[1,2-b]-thiophen-2-carboxylic acid, 21.6parts 1-amino-2-hydroxy-5-dimethylaminosulphonyl-benzene and 2 partsboric acid are heated in 40 parts diethylene glycol diethyl ether undera weak nitrogen current, while stirring and distilling off the liquid,at 180-190 for 30 minutes and at 200 for 15 minutes. The solidifiedyellow mass is cooled, heated at boiling temperature under reflux for 15minutes with 50 parts by volume phosphorus oxychloride, and poured on to3 00 parts of ice and 200 parts of water. The mixture is subsequentlyneutralized with a sodium hydroxide solution while cooling. Theresultant crystalline precipitate is filtered off with suction, washedwith water and recrystallized from 300 parts methyl glycol. For furtherpurification, the compound is dissolved hot in 200 parts chlorobenzene,the solution clarified with 1 part tonsil and, after filtering, theproduct is precipitated with 300 parts methanol. 13.2 parts of thecompound of the formula and of melting point 234-235 are obtained.

The following compound is obtained in an analogous way with the use ofthe corresponding starting compounds: (18) I SOr-N S H2)a Ha meltingpoint: 182-183 9 EXAMPLE 7 24.4 partsmethyl-4,S-dihydronaphtho-[1,2-b]-thiophen-2-carboxylic acid are heatedat boiling temperature under refiux for minutes with 100 parts ofthionyl chloride which has been distilled over linseed oil, a clearsolution being formed. The excess of thionyl chloride is subsequentlyremoved in a vacuum. The residue is taken up with 300 parts by volume ofdry xylene. 17 parts 1- amino-Z-hydroxybenzene-S-carboxylic acid methylester are added at room temperature while stirring. The mixture isheated at boiling temperature for 16 hours, while hydrogen chlorideescapes. The resultant crystalline precipitate is filtered ofi withsuction at 80, washed with methanol, and dried at 70 in a vacuum. 22.6parts of the compound of the formula (19) H HO CHa II t C C 0 0 CH S NHand of melting point 278-279 are obtained.

8 parts of the compound of the Formula 19 are mixed with 0.5 part boricacid and heated under nitrogen at 290- 300 for one hour while waterescapes. The melt is mixed with 3 parts by volume dimethyl formamide,starting at 170, and with 35 parts by volume methanol, starting at 90and cooling under reflux, and it is subsequently stirred on an ice bathuntil cold. The resultant crystalline precipitate is filtered off withsuction, washed with methanol, and dried at 70 in a vacuum. 6.5 parts ofa compound of the formula CH3[/\ N o 0 0 CH3 8 and of melting point163-166 are obtained. After dissolving in 50 parts by volumechlorobenzene, clarification with 1 part tonsil, concentration andprecipitation with methanol, the compound melts at 163-165 The followingcompounds are prepared in an analogous way with the use of thecorresponding starting commelting point: 193-195" melting point: 130133(23) OULKKDCOOCHPQ melting point: 180-181 lt tj melting point: 204-206EXAMPLE 8 Polyester fibres produced from terephthalic acid and ethyleneglycol are introduced in a liquor ratio of 1:40 into an aqueous bathcontaining, per litre, 1 g. sodium oleyl sulphate and 0.075 g. of thecompound of the Formula 16 as brightening agent. The bath is heated toboiling temperature and kept at this temperature for 45-60 minutes.After rinsing and drying, the polyester fibres exhibit a very goodbrightening elfect which is fast to light.

It is also possible to work with advantage in the presence of 2 g. perlitre of a commercial dye carrier of the type of trichlorobenzene.

Very good brightening effects are also achieved on polyester fibres whenthe brightening agent mentioned above is replaced with one of thefollowing compounds: Compound of the Formulae 1, 10, 11, 13, 14, 15, 17,18, 20, 24.

EXAMPLE 9' Polyamide fibres of ecaprolactam are introduced in a liquorratio of 1:30 at 60 into an aqueous bath containing, per litre, l g.sodium oleyl sulphate and 0.1 g. of the compound of the Formula 10 asbrightening agent. The bath is heated at 95 for 60 minutes, and thefibres are then rinsed and dried. They exhibit an excellent brighteningelfect. Very good brightening effects are also obtained on polyamidefibres, when the brightening agent mentioned above is replaced with oneof the following compounds: Compounds of the Formulae 3, 5, 7, 8, 9, 11,22.

EXAMPLE 10 Cellulose acetate fibres (2- /2-acetate) are moved about in aliquor ratio of 1:30 at 70 in an aqueous bath containing, per litre, 1g. of a commercial interface-active paraffin sulphonate and 0.07 g. ofthe compound of the Formula 1 as brightening agent. The fibres aresubsequently rinsed and dried. They then exhibit a very good brighteningeffect. Very good brightening effects are also ob tained on celluloseacetate fibres when the brightening agent mentioned above is replacedwith one of the following col'npoundsz 7),

EXAMPLE 1 1 Cellulose triacetate fibres are introduced in a liquor ratioof 1:30 into an aqueous bath containin per litre, l g. of a commercialinterface-active parafiin sulphonate and 0.07 g. of the Compound 13 asbrightening agent. The bath is then heated to -95 and kept at thistemperature for 40 minutes. The fibres are subsequently rinsed anddried. They then exhibit a very good brightening elfect. Very goodbrightening effects are also obtained on cellulose triacetate fibreswhen the brightening agent mentioned above is replaced with one of thefollowing compounds: (6), (10), (11), (17), (18).

EXAMPLE 12 Polypropylene fibres are introduced in a liquor ratio of 1:30into an aqueous lbath containing, per litre 1 g. of a commercialinterface-active paraffin sulphonate and 0.07 g. of the compound of theFormula 10 as brightening agent. The bath is heated at 95 for 30 minutesand the fibres are subsequently rinsed and dried. They exhibit a goodbrightening effect. Good brightening effects are also obtained onpolypropylene fibres when the brightening agent mentioned above isreplaced with one of the following compounds: Compound of the Formulae1, 6, l1.

EXAMPLE 13 65 parts of a polyvinyl chloride powder prepared by emulsionpolymerization, 35 parts of a commercial dioctyl phthalate asplasticizer, 2 parts of a commercial tin dilaurate as stabilizer, and0.05 part of the compound of the Formula 6 are stirred to form a pasteand subsequently rolled in a three-roll calender at 160-170 to produce afoil. The foil then exhibits an excellent brightening effect which isfast to light. Similar brightening effects are achieved when thebrightening agent mentioned above is replaced with one of the followingcompounds: Compound of the formulae 1, 3, 10, 11.

EXAMPLE 14 100 parts of a high pressure polyethylene granulate and 0.05part of the Compound 10 are intimately mixed in a vibration mixer andsubsequently extruded in an extruder at ISO-210 via a slot die toproduce a foil of between 50 and 100g thickness. The foil exhibits anexcellent brightening efiect. The brightening agent is completely fastto migration in polyethylene. Similar good brightening effects areachieved when the brightening agent mentioned above is replaced with oneof the following compounds: Compound of the Formula 1, 6, 11.

EXAMPLE 15 100 parts of polypropylene granulate are intimately mixed ina vibration mixer with 0.05 part of the Compound 3 and 1 part titaniumdioxide (rutile), and subsequently extruded in an extruder at 1802l0 viaa slot die to produce a 'foil of between 50 and 100,41. thickness. Thefoil exhibits an excellent brightening effect. The brightening agent iscompletely fast to migration in polypropylene. Similar good brighteningeffects are achieved when the brightening agent mentioned above isreplaced with one of the following compounds: Compound of the formulae1, 5, 6, 8, '9, 10,11,18.

EXAMPLE 16 100 parts of polystyrene granulate are rolled on a hot rollto produce a rough sheet. 1 part titanium dioxide (rutile) and 0.1 partof the compound of the Formula 11 are then rolled in. The rolled mass issubsequently worked up in a cross-beater mill to produce a finelydivided granulate. Mouldings with smooth surfaces are produced therefrom!by means of an injection moulding machine. The mouldings exhibit anexcellent degree of whiteness. Similar good brightening effects areachieved when the brightening agent mentioned above is replaced with oneof the following compounds: Compound of the Formulae 6, l0.

EXAMPLE 17 100 parts of a fabric of poly-e-caprolactam fibres areimpregnated at room temperature with a clear padding liquor consistingof 3 parts of the compound of the Formula 10 and 997 parts oftetrachloroethylene. After squeezing to a weight increase of 64%, thefabric is dried at 80 for 1 minute and subsequently heated at 190-182 C.for 45 seconds. The fabric thus treated exhibits a very good brighteningeffect with good fastness properties.

12 EXAMPLE 1s A fabric of polyamide fibres is washed in a liquor ratioof 1:20 at 60 for 15 minutes with a washing liquor containing, perlitre, 5 g. of a washing powder with which 0.2% of the brightening agentof the Formula 2 have been incorporated in the usual way in finelydivided form. The washing powder has the following composition:

Percent Sodium dodecylbenzene-sulphonate 10.0 Nonionic of nonyl phenoland ethylene oxide (molar ratio 1:20) 2.5 Soap flakes 3.5 Carboxy-methylcellulose 1.5 Sodium tripolyphosphate 45.0 Sodium silicate (dry) 5.0Sodium sulphate (10 H O) 32.5

After rinsing and drying, the polyamide fabric exhibits a substantiallyhigher degree of whiteness than before washing. By repeated washingunder the stated conditions the degree of whiteness of the polyamidefabric is increased even further (up to the 5th washing).

The brightening effects achieved are outstandingly fast to light andfast to chlorine.

EXAMPLE 19 Polyacrylonitrile fibres are introduced in a liquor ratio of1:40 into an aqueous rbath containing, per litre, l g. of a commercialoleyl polyglycol ether, 1 g. oxalic acid, 0.5 g. of a 36% sodiumbisulphite solution, and 0.075 g. of the compound of the Formula 13 asbrightening agent. The bath is heated to boiling temperature within 20minutes and kept at this temperature for 1 hour. The polyacrylonitrilefibres are subsequently rinsed and dried. They then exhibit an excellentbrightening effect.

I claim:

1. A benzoxazole of the formula zyl, phenylisopropyl, phenyl, carboxylicacid methylester, carboxylic acid butyl ester, carboxylic acidbenzylester, ethylsulfonyl, dimethylaminosulfonyl, diethylaminocarbonyl,or dibutylaminosulfonyl; and

Z and Z are hydrogen or methyl.

2. A benzoxazole of claim 1 having the formula:

3. A benzoxazole of claim 1 having the formula:

13 4. A benzoxazole of claim 1 having the formula: 7. A benzoxazole ofclaim 1 having the formula:

We W1 10 8. A benzoxazole of claim 1 having the formula:

5. A benzoxazole of claim 1 having the formula:

20 References Cited UNITED STATES PATENTS 3,255,199 6/ 1966 Maeder et al260--307 6. A benzoxazole of claim 1 having the formula: 3,452,0366/1959 Cracker et 25 3,557,121 1/1971 Faith 260--281 3,565,890 2/1971Tanaka 260240 US. Cl. X.R.

N m/ 01 ALEX MAZEL, Primary Examiner \3 R. V. RUSH, Assistant Examiner

